Organic acids and oligomers thereof have been shown to promote plant growth. Typical such regulators of plant growth are described by Kinnersley et al., Plant Growth Regulation 9:137-146 (1990), which publication mentions the effects of lactic acid and relatively low molecular weight oligomers of lactic acid on plant growth. Similar description is found in U.S. Pat. No. 4,813,997 to Kinnersley et al. (oligomers of glycolic and/or L-lactic acid) and U.S. Pat. No. 4,799,957 to Danzig et al. (oligomers of thiolactic and thioglycolic acids). All of the forgoing approaches to plant growth enhancement appear to focus on chelation as a means for enhancing plant uptake of compounds vital to the growth of the plant, e.g., micronutrients such as calcium, magnesium, sulfur, manganese, zinc, copper, iron, boron, and the like.
A very common approach to the enhancement of plant growth has been, and continues to be, the use of fertilizers, natural as well as synthetic. The latter usually provide nitrogen in a plant-usable form, such as urea for example, and/or inorganic nitrates, phosphates, or the like compounds. While such fertilizers may be applied, more or less, at the convenience of the farmer, and may be applied as often as deemed desirable, the overuse of synthetic fertilizers is a major factor responsible for environmental problems such as eutrophication of ground water, nitrate pollution, phosphate pollution, and the like. An overview of the undesirable effects of nitrogen fertilizers is presented by Byrnes, Fertilizer Research 26:209-215 (1990).
To ameliorate the problems attendant to fertilizer overuse, it would be desirable to increase fertilizer efficiency. The present invention addresses these problems, and provides compositions and methods for enhancing the fertilizer uptake efficiency of plants.